Improved performance of UV-blue dual-band Bi2O3/TiO2 photodetectors and application of visible light communication with UV light encryption

Abstract

In this paper, self-powered photodetectors (PDs) with a dual-band photoresponse and excellent photodetection capabilities in complex environments can meet the needs of diverse detection targets, complex environments and diverse tasks. Herein, Bi₂O₃ nanosheets were deposited on the surface of TiO₂ nanorod arrays (NRs) by chemical bath deposition (CBD) to construct self-powered heterojunction PDs with a UV-blue dual-band photoresponse. The nucleation and growth of Bi₂O₃ nanosheets on TiO₂ NRs substrates were controlled by varying the concentration of the complexing agent triethanolamine (TEA) in the precursor solution, which regulated the morphology, crystalline quality and energy band structure as well as the photoelectronic properties of Bi₂O₃ films. The devices fabricated at a TEA concentration of 0.3 M exhibited excellent self-powered UV-blue dual-band photoresponse characteristics, achieving a photocurrent (I_ph) of 144 nA, a responsivity of 1.79 mA W⁻¹ and a detectivity of 5.94 × 10¹⁰ Jones under 405 nm illumination at 0 V, which can be attributed to the large built-in electric field (E_b) of Bi₂O₃/TiO₂ heterojunctions, the low interfacial transfer resistance and suitable carrier transport path. In addition, Bi₂O₃/TiO₂ heterojunction PDs with the UV-blue dual-band photoresponse characteristics can be applied in UV-encrypted visible light communication (VLC) with a light-controlled logic gate to improve the security of information transmission.